1. Field of the Invention
The present invention relates to a method and device for determining the particle size category of particles dispersed in a liquid, also the categories of different materials simultaneously dispersed in the liquid and having different average particle sizes.
2. Description of the Prior Art
Previously known similar methods in which the sample is in the form of a suspension or a solution are usually based on optical observation, the use of ultrasonic methods, or the use of the centrifugal force or gravity affecting the particles in the liquid.
The disadvantage of optical observation is that the multitude of small particles saturates the device and complicates the obtaining of a sufficiently transparent sample.
The disadvantage of ultrasonic devices is their sensitivity to small air bubbles and the complexity of the devices in general.
It is also appropriate to note in this connection that these known optical and ultrasonic methods by no means aim at obtaining a certain areal distribution of the particles, which is the case in the present invention, as described below.
The previously known devices which are based on a centrifugal force or gravity affecting the particles have a disadvantage in that the velocity of the particles is proportional to their density and the second power of their diameter even in an ideal case. Therefore it is difficult, for example, to determine the size of particles with varying density.
Also known is a device in which a suspension flows along a horizontal gutter provided with a measuring rod which moves reciprocally in the vertical direction against a stop at the bottom of the gutter; this rod senses the size of a particle left between the rod and the stop. This device has a substantial disadvantage in that it is capable of measuring the sizes of only the largest particles.
Furthermore, by no known method is it possible to determine separately the sizes of particle categories with different chemical compositions when they are mixed with each other.